A common Protestant position, though not held by all Protestant denominations (Lutherans for instance), is that baptism is merely a symbolic event of a Christian's life rather than being an integral sacrament necessary for salvation. Before going forward let us look to the Catholic Encyclopedia for a definition and explanation of baptismal regeneration.
"Regeneration is a Biblico-dogmatic term closely connected with the ideas of justification, Divine sonship, and the deification of the soul through grace. Confining ourselves first to the Biblical use of this term, we find regeneration from God used in indissoluble connection with baptism, which St. Paul expressly calls "the laver of regeneration" (Titus 3:5). In His discourse with Nicodemus (John 3:5), the Saviour declares: "Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God." In this passage Christianity from its earliest days has found the proof that baptism may not be repeated, since a repeated regeneration from God is no less a contradiction than repeated physical birth from a mother. The idea of "birth from God" enjoys a special favour in the Joannine theology. Outside the Fourth Gospel (1:12 sq.; 3:5), the Apostle uses the term in a variety of ways, treating "birth of God" as synonymous now with the "doing of justice" (1 John 5:1, 4 sq.), and elsewhere deducing from it a certain "sinlessness" of the just (1 John 3:9; 5:18), which, however, does not necessarily exclude from the state of justification the possibility of sinning (cf. Bellarmine, "De justificatione", III, xv).
"It is true that in all these passages there is no reference to baptism nor is there any reference to a real "regeneration"; nevertheless, "generation from God", like baptismal "regeneration", must be referred to justification as its cause. Both terms effectually refute the Protestant notion that there is in justification not a true annihilation, but merely a covering up of the sins which still continue (covering-up theory), or that the holiness won is simply the imputation of the external holiness of God or Christ (imputation theory)."
- The Catholic Encyclopedia (J. Pohle Regeneration)
Baptismal regeneration is an apostolic belief rooted in tradition and scripture. The latter root is what Protestants will reject, but they do not reject that the early church believed in such a teaching. As Zwingli, the Swiss reformer stated
“In this matter of baptism — if I may be pardoned for saying it — I can only conclude that all the doctors have been in error from the time of the apostles." - Huldrych Zwingli (“On Baptism,” Zwingli and Bullinger, Vol. 24, p. 130)
It is quite bold to state that one can interpret and understand scripture and the apostolic teachings better than those early generations of Christians while being over a millenia and a half removed from the beginning of the Church. Though, that is what one must do when contradicting that which the Early Church had received and passed on.
The Early Church can supply an enriching insight into the direct affect of the ministry of the Apostles and their disciples, and how the teachings of the Apostolic Age carried on within the heart of the Church. Because of this, Pope Benedict XVI said:
"What earlier generations held as sacred, remains sacred and great for us too” (July 7, 2007)
So with that let us look to the early periods of the Church and allow them to speak for themselves on this matter.
Theophilus, Patriarch of Antioch
“Moreover, those things which were created from the waters were blessed by God, so that this might also be a sign that men would at a future time receive repentance and remission of sins through water and the bath of regeneration–all who proceed to the truth and are born again and receive a blessing from God” (To Autolycus 12:16 [A.D. 181]).
St. Justin Martyr
“Whoever are convinced and believe that what they are taught and told by us is the truth, and professes to be able to live accordingly, is instructed to pray and to beseech God in fasting for the remission of their former sins, while we pray and fast with them. Then they are led by us to a place where there is water, and they are reborn in the same kind of rebirth in which we ourselves were reborn: In the name of God, the Lord and Father of all, and of our Savior Jesus Christ, and of the Holy Spirit, they receive the washing of water. For Christ said, ‘Unless you be reborn, you shall not enter the kingdom of heaven.’…The reason for doing this, we have learned from the Apostles” (The First Apology 61:14-17 [inter A.D. 148-155]).
“A treatise on our sacrament of water, by which the sins of our earlier blindness are washed away and we are released for eternal life will not be superfluous…. Taking away death by the washing away of sins. The guilt being removed, the penalty, of course, is also removed…. Baptism itself is a corporal act by which we are plunged into the water, while its effect is spiritual, in that we are freed from our sins” (On Baptism 1:1, 5:6, 7:2 [inter A.D. 200-206]).
St. Clement of Alexandria
"When we are baptized we are enlightened. Being enlightened, we are adopted as sons. Adopted as sons, we are made perfect. Made perfect, we become immortal… ‘and sons of the Most High’ [Ps. 81:6]. This work is variously called grace, illumination, perfection, and washing. It is a washing by which we are cleansed of sins, a gift of grace by which the punishments due our sins are remitted, an illumination by which we behold that holy light of salvation–that is, by which we see God clearly, and we call that perfection which leaves nothing lacking. Indeed, if a man know God, what more does he need? Certainly, it were out of place to call that which is not complete a true gift of God’s grace. Because God is perfect the gifts he bestows are perfect” (The Instructor of Children, 1:6:26:1 [ante A.D. 202]).
“Formerly there was baptism in an obscure way…now, however, in full view, there is regeneration in water and in the Holy Spirit. Formerly, in an obscure way, there was manna for food; now, however, in full view, there is the true food, the flesh of the Word of God, as he himself says: ‘My flesh is true food, and my blood is true drink’ (John 6:56) (Homilies on Numbers 7:2 [post A.D. 244]).“The Church received from the apostles the tradition of giving baptism even to infants. For the apostles, to whom were committed the secrets of divine mysteries, knew that there is in everyone the innate stains of sin, which are washed away through water and the Spirit” (Commentaries on Romans 5:9 [Post A.D. 244]).
St. Cyprian of Carthage
“But afterwards, when the stain of my past life had been washed away by means of the water of rebirth, a light from above poured itself upon my chastened and now pure heart; afterwards, through the Spirit which is breathed from heaven, a second birth made of me a new man” (To Donatus 4 [circa A.D. 246]).
“From baptism we receive the spirit of Christ. At that same moment in which the priests invoke the Spirit, heaven opens, and he descends and rests upon the waters, and those who are baptized are clothed in him. The Spirit is absent from all those who are born of the flesh, until they come to the water of rebirth, and then they receive the Holy Spirit….[I]n the second birth, that through baptism, they receive the Holy Spirit” (Treatises 6:14:4 [inter A.D. 336-345]).
St. Cyril of Jerusalem
“If any man does not receive baptism, he does not have salvation. The only exception is the martyrs, who, even without water, will receive baptism, for the Savior calls martyrdom a baptism (cf. Mark 10:38)….Bearing your sins, you go down into the water; but the calling down of grace seals your soul and does not permit that you afterwards be swallowed up by the fearsome dragon. You go down dead in your sins, and you come up made alive in righteousness” (Catechetical Lectures 3:10,12 [circa A.D. 350]).
“For prisoners, baptism is ransom, forgiveness of debts, death of sin, regeneration of the soul, a resplendent garment, an unbreakable seal, a chariot to heaven, a protector royal, a gift of adoption” (Sermons on Moral and Practical Subjects: On Baptism 13:5 [ante A.D. 379]).
“The Lord was baptized, not to be cleansed himself but to cleanse the waters, so that those waters, cleansed by the flesh of Christ which knew no sin, might have the power of baptism. Whoever comes, therefore, to the washing of Christ lays aside his sins” (Commentary on the Gospel of Luke 2:83 [circa A.D. 389]).
“This much you must know, that baptism forgives past sins, but it does not safeguard future justice, which is preserved by labor and industry and diligence and depends always and above all on the mercy of God” (Dialogue Against the Pelagians 3:1 [A.D. 415]).
St. Augustine of Hippo
“By this grace baptized infants too are ingrafted into his [Christ’s] body, infants who certainly are not yet able to imitate anyone. Christ, in whom all are made alive,…gives also the most hidden grace of his Spirit to believers, grace which he secretly infuses even into infants….It is an excellent thing that the Punic [North African] Christians call baptism salvation and the sacrament of Christ’s Body nothing else than life. Whence does this derive, except from an ancient and, as I suppose, apostolic tradition, by which the Churches of Christ hold inherently that without baptism and participation at the table of the Lord it is impossible for any man to attain either to the kingdom of God or to salvation and life eternal? This is the witness of Scripture too…If anyone wonders why children born of the baptized should themselves be baptized, let him attend briefly to this…The sacrament of baptism is most assuredly the sacrament of regeneration” (Forgiveness and the Just Deserts of Sin, and the Baptism of Infants 1:9:10; 1:24:34; 2:27:43 [A.D. 412]).
The Epistle of Barnabas
“Now let us see if the Lord has been at any pains to give us a foreshadowing of the waters of baptism and of the cross. Regarding the former, we have the evidence of Scripture that Israel would refuse to accept the washing which confers the remission of sins and would set up a substitution of their own instead [Jer. 22:13; Is. 16:1-2, 33:16-18; Ps. 1:3-6].
Observe there how he describes both the water and the cross in the same figure. His meaning is, `Blessed are those who go down into the water with their hopes set on the cross.’ Here he is saying that after we have stepped down into the water, burdened with sin and defilement, we come up out of it bearing fruit, with reverence in our hearts and the hope of Jesus in our souls” (11:1-10 [circa A.D. 70]).
" ‘I have heard, sir,’ said I, ‘from some teacher, that there is no other repentance except that which took place when we went down into the water and obtained the remission of our former sins.’ He said to me, ‘You have heard rightly, for so it is'” (The Shepherd 4:3:1-2 [A.D. 140]).
“They had need [the Shepherd said] to come up through the water, so that they might be made alive, for they could not otherwise enter into the kingdom of God, except by putting away the mortality of their former life. These also, then, who had fallen asleep, received the seal of the Son of God and entered into the kingdom of God. For,’ he said, ‘before a man bears the name of the Son of God, he is dead. But when he receives the seal he puts mortality aside and again receives life. The seal, therefore, is the water. They go down into the water dead [in sin], and come out of it alive” (Ibid. 9:16:2-4).